Wide ranges of medical treatments have been developed using endoluminal prostheses, which are medical devices adapted for temporary or permanent implantation within a body lumen, such as naturally occurring or artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include arteries such as those located within coronary, mesentery, peripheral, or cerebral vasculature; arteries; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes. Various types of endoluminal prostheses have also been developed with particular structures to modify the mechanics of the targeted lumen wall.
A number of vascular devices have been developed for replacing, supplementing, or excluding portions of blood vessels. These vascular devices include endoluminal vascular prostheses and stent grafts. Aneurysm exclusion devices, such as abdominal aortic aneurysm (AAA) devices, are used to exclude vascular aneurysms and provide a prosthetic lumen for the flow of blood. Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually from disease or a genetic predisposition, which can weaken the arterial wall and allow it to expand. Aneurysms can occur in any blood vessel, but most occur in the aorta and peripheral arteries, with the majority of aneurysms occurring in the abdominal aorta. An abdominal aneurysm typically begins below the renal arteries and extends into one or both of the iliac arteries.
Aneurysms, especially abdominal aortic aneurysms, have been commonly treated in open surgery procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While open surgery is an effective surgical technique in light of the risk of a fatal abdominal aortic aneurysm rupture, the open surgical technique suffers from a number of disadvantages. It is complex, requires a long hospital stay, requires a long recovery time, and has a high mortality rate. Less invasive devices and techniques have been developed to avoid these disadvantages. Tubular endoluminal prostheses that provide a lumen or lumens for blood flow while excluding blood flow to the aneurysm site are introduced into the blood vessel using a catheter in a less or minimally invasive technique. The tubular endoluminal prosthesis is introduced in a small diameter compressed configuration and expanded at the aneurysm. Although often referred to as stent grafts, these tubular endoluminal prostheses differ from so called covered stents in that they are not used to mechanically prop open stenosed natural blood vessels. Rather, they are used to secure graft material in a sealing engagement with the vessel wall and to prop open the tubular passage through the graft without further opening the abnormally dilated natural blood vessel.
Stent grafts for use in abdominal aortic aneurysms typically include a support structure supporting woven or interlocked graft material. Examples of woven graft materials are woven polymer materials, e.g., Dacron, or polytetrafluoroethylene (PTFE). Interlocked graft materials include knit, stretch, and velour materials. The graft material is secured to the inner or outer diameter of the support structure, which supports the graft material and/or holds it in place against a vessel wall. The stent graft is secured to a vessel wall above and below the aneurysm. A proximal spring stent of the stent graft can be located above the aneurysm to provide a radial force to engage the vessel wall and seal the stent graft to the vessel wall.
One problem is that stent grafts can migrate over time after installation in the vessel. The stent graft is subject to a variety of loads due to the force associated with blood flowing through the stent graft, and the pulsatile pressure causing expansion and contraction of arteries. Changes in the anatomy of the abdominal aortic aneurysm can contribute to the cause of migration. One attempt to prevent migration has provided the proximal spring stent with tines, barbs, hooks, and the like to puncture the vessel wall and secure the stent graft in place. Unfortunately, the wall area for prosthesis fixation above an aneurysm or other diseased vessels may be limited, making secure fixation of the prosthesis more difficult. When using hooks, each hook is attached at a single point, so the loading on the vessel wall and the hook is concentrated at the single point. Hydrodynamic loading can dislodge one or more of the hooks from the vessel wall over time and allow migration, exposing the aneurysm to blood pressure and leakage flow. The hooks are also attached to fixed positions spaced around the periphery of the stent graft, so that a poor seal and leakage occurs when the hook is not set to the required depth.
Another problem is that stent grafts can block blood flow to side branches off the vessel in which the stent graft is deployed. For thoracic aortic aneurysms (TAA) in the aortic arch, one or more of the innominate, left common carotid, and left subclavian arteries can be at or near the aneurysm. The location of the arteries can preclude use of a stent graft or limit where the stent graft can be deployed since blood flow to these major arteries must be maintained. The location of the arteries can also limit where hooks can be placed to fix the stent graft to the vessel wall, so that a poor seal and leakage occurs.
It would be desirable to overcome the above disadvantages.